Integration of III-V membranes on silicon-on-insulator (SOI) substrates offers a promising route to provide on-chip gain for dense silicon (Si) photonics. Here, we present a materials study of InP membranes with embedded InGaAs multi-quantum wells (MQWs) directly grown above the Si waveguide layer via a tunnel epitaxy process. Cross-sectional scanning transmission electron microscopy (STEM), combining differential phase contrast (DPC) imaging, energy-dispersive X-ray spectroscopy (EDX), and atomic-column-based strain analysis, confirms high-quality laterally grown InP membranes with defects confined to the V-groove region and elucidates facet-dependent MQW formation on (111)A, (110), and (111)B facets. Both EDX and strain analysis consistently reveal high-In, highly compressively strained (110) QWs (>80% In), and no misfit dislocations are observed at InP/InGaAs interfaces. In addition, under identical precursor ratios, ultra-thin QWs incorporate a higher indium composition than a thick bulk InGaAs region. These results provide practical guidance for designing efficient active regions in future electrically injected, Si-waveguide-coupled InP membrane lasers on SOI.
Yan et al. (Tue,) studied this question.